CODEWITHSUNDEEP
linuxbashunix
tony19
tony19

Reputation: 138286

bash: simpler way to get multiple elements of array at once?

Is there a *nix command that formats input (delimited by newlines) so that only a specific max number of elements appear per line? For example:

$ yes x | head -10 | command 4
x x x x
x x x x
x x

I wrote a quick bash script (shown below) that performs this task, but it seems long and probably inefficient. Is there a better way to do this?

#!/bin/sh

if [ -z "$1" -o -z "$2" ]; then
        echo Usage `basename $0` {rows} {columns}
        exit 1
fi

ROWS=$1
COLS=$2

input=$(yes x | head -${ROWS})
lines=()
i=0
j=0
eol=0

for x in ${input[*]}
do
        lines[$i]="${lines[$i]} $x"
        j=`expr $j + 1`
        eol=0
        if [ $j -ge ${COLS} ]; then
                echo lines[$i] = ${lines[$i]}
                i=`expr $i + 1`
                j=0
                eol=1
        fi
done

if [ ${eol} -eq 0 ]; then
        echo lines[$i] = ${lines[$i]}
fi

Upvotes: 4

Views: 7970

Answers (5)

cnst
cnst

Reputation: 27218

You can use xargs(1) for this, with the -n or --max-args= option to limit the number of arguments per command line:

$ yes x | head -10 | xargs -n4
x x x x
x x x x
x x
$

Obviously, you have to be able to trust the input; for example, xargs famously breaks if the quotes are not matched:

$ yes 'x"' | head -10 | xargs -n4
xargs: unmatched double quote; by default quotes are special to xargs unless you use the -0 option
$

Upvotes: -1

mawia
mawia

Reputation: 9349

why dont you try something like 

sed 's|\(.{10}\)|\1\n|'

I'working on Window machine and have not tried this.My idea is just match everything for N number of times and replace them with matched pattern plus new line character.

P.S Please correct the sed expression for any syntatic fault.

Upvotes: 0

Dennis Williamson
Dennis Williamson

Reputation: 360105

printf '%-10s%-10s%-10s%s\n' $(command | command)

printf will consume the number of arguments specified in the format string at a time and continue until they're all consumed.

Demonstration:

$ printf '%-10s%-10s%-10s%s\n' $(yes x | head -n 10)
x         x         x         x
x         x         x         x
x         x
$ printf '%-10s%-10s%-10s%s\n' $(<speech)
now       is        the       time
for       all       good      men
to        come      to        the
aid       of        their     country

Upvotes: 5

mVChr
mVChr

Reputation: 50185

yes x | head -10 | awk 'BEGIN { RS = "%%%%%%%" } { split($0,a,"\n"); for (i=1; i<length(a); i+=4) print a[i], a[i+1], a[i+2], a[i+3] }'

More readable:

yes x | \
head -10 | \
awk 'BEGIN { RS = "%%%%%%%" }
     { split($0,a,"\n"); 
       for (i=1; i<length(a); i+=4) print a[i], a[i+1], a[i+2], a[i+3] }'

Upvotes: 1

Ignacio Vazquez-Abrams
Ignacio Vazquez-Abrams

Reputation: 798676

Arrays can be sliced.

$ foo=(q w e r t y u)
$ echo "${foo[@]:0:4}"
q w e r

Upvotes: 8

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